Heavy Construction News – Newly discovered ‘Casper’ octopod at risk from deep-sea mining — ScienceDaily

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Last spring, researchers made headlines with the discovery of what was surely a new species of octopod, crawling along the seafloor at a record-breaking ocean depth of more than 4,000 meters (about 2.5 miles) off Necker Island near Hawaii. The octopod’s colorless and squishy appearance immediately inspired the nickname “Casper.” Now, a report published in Current Biology on December 19 reveals that these ghost-like, deep-sea octopods lay their eggs on the dead stalks of sponges attached to seafloor nodules rich in the increasingly valuable metals used in cell phones and computers.

“Presumably, the female octopod then broods these eggs, probably for as long as it takes until they hatch — which may be a number of years,” says Autun Purser of the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research in Germany.

“The brooding observation is important as these sponges only grow in some areas on small, hard nodules or rocky crusts of interest to mining companies because of the metal they contain,” including manganese, he adds. “The removal of these nodules may therefore put the lifecycle of these octopods at risk.”

Purser explains that the deep-sea manganese nodules form similarly to pearls in an oyster. In a process that could take millions of years, metals gradually build up in rocky layers onto a small starting seed, perhaps a shell fragment or a shark’s tooth.

“These nodules look a bit like a potato, and are made up of rings of different shells of metal-rich layers,” Purser says. “They are interesting to companies as many of the metals contained are ‘high-tech’ metals, useful in producing mobile phones and other modern computing equipment, and most of the land sources of these metals have already been found and are becoming more expensive to buy.”

Purser says that little was known about the creatures found in the deep-sea environments where those attractive metals are found. In a series of recent cruises, the researchers set out to find the organisms that live there and to understand how the ecosystem and animals might be impacted by mining activities.

Their studies have shown that octopods are numerous in manganese crust areas, precisely where miners would hope to extract metals of interest. The mineral-biota association that they observed is a first for any octopod lacking fins (a group known as incirrate octopods), and it puts these captivating octopods, which live their long lives at a slow pace, at particular risk.

“As long-lived creatures, recovery will take a long time and may not be possible if all the hard seafloor is removed,” Purser says. “This would be a great loss to biodiversity in the deep sea and may also have important knock on effects. Octopods are sizable creatures, which eat a lot of other smaller creatures, so if the octopods are removed, the other populations will change in difficult to predict ways.”

Purser says that he and his colleagues continue to study the nodules and their importance to microbes and animals both small and large, including starfish, crabs, and fish.

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When it comes to extremely fine, precise features, a scanning electron microscope (SEM) is unrivaled. A focused electron beam can directly deposit complex features onto a substrate in a single step (Electron-Beam-Induced Deposition, EBID). While this is an established technique for gold, platinum, copper and further metals, direct electron beam writing of silver remained elusive. Yet, the noble metal silver promises especially interesting potential applications in nano-optics in information technology. For the first time a team from the HZB and the Swiss Federal Laboratories for Materials Science and Technology (EMPA) has successfully realized the local deposition of silver nanocrystals by EBID. The results have now been published in the journal of the American Chemical Society’s ACS Applied Materials Interfaces.

Challenging chemistry

The chemistry of typical silver compounds is extremely challenging. They are difficult to evaporate and are highly reactive. During the heating in the injection unit, they tend to chemically react with the reservoir walls. Along their path from the reservoir to the tip of the needle, these compounds freeze again at the slightest drop in temperature and obstruct the tube. “It took us a lot of time and effort to design a new injection unit and find a suitable silver compound,” explains HZB physicist Dr. Katja Höflich, who carried out the experiments as part of a Helmholtz Postdoctoral Fellowship at EMPA. “Finally, we managed it. The compound silver dimethylbutyrate remains stable and dissociates only in the focus of the electron beam.” Höflich and her colleagues used the EBID method to create sharply defined areas of tiny silver nanocrystals for the first time.

Writing with the electron beam

The principle works as follows: tiny amounts of a precursor substance — typically a metal-organic compound — are injected into the vacuum chamber of the SEM near the surface of the sample using a needle. Where the electron beam hits the sample surface, the precursor molecules dissociate and their non-volatile constituents are deposited in place. The electron beam can move like a pen over the substrate to create the desired features. For many precursor substances this works even in three dimensions.

Silver is a light concentrator

The fabricated silver nanostructures possess remarkable optical properties: visible light can excite the free electrons in the metal into oscillations referred to as plasmons. Plasmons are accompanied by an extreme lighting. Information about the composition of the surfaces can be obtained from the colour and intensity of this scattered light. This effect can be utilised in Raman spectroscopy to detect the fingerprint of specific molecules that bind to the silver surface — down to the level of a single molecule. Hence, silver nanostructures are good candidates as sensors for explosives or other dangerous compounds.

A vision for the future: components for optical computing

Further applications are conceivable in future information technology: complex silver nanostructures may constitute the basis for purely optical information processing. To realize this, the process has to be refined, such that complex features can be directly written as already possible for other precursor compounds.

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